The hazards of glass breakage in homes, businesses and automobiles can be caused by a number of factors. For example, vandalism, theft, hurricanes, tornadoes, wind-blown debris, bullets, and explosions, such as bomb blasts, petro-chemical accidents, and industrial accidents, can cause glass breakage. Flying glass resulting from the glass breakage can lead to human loss of life, as well as injury. Flying glass tends to cause upwards 80% of the casualties in bomb blasts from terrorism, such as the Alfred P. Murrah building in Oklahoma City, according to reports from the Department of Homeland Security.
Commercially available glass is made up of 4 basic types: soda lime, lead glass, borosilicate glass, and alumina silicate glass. Soda lime is the least costly, and most used commercially. Lead Glass is brilliant and tough. Borosilicate Glass has high heat and chemical resistance. Alumina Silicate Glass has the highest heat and chemical resistance of the four.
For most applications, soda-lime is the most commercially used and consequently has the greatest issues derived from flaws introduced into glass at the microscopic level. When glass is cooled, there appears on the surfaces of both sides in many cases, micro-fissures or micro-cracks or predisposed fault lines that inherently weaken glass. These micro-fissures/micro-cracks cause glass to break or fracture along these predisposed fault lines when external forces are applied, in the form of various types of impacts or impulse and/or overpressure.
A conventional solution for strengthening glass is to chemically temper the flat glass plate, for example with tri-potassium phosphate via introduction of the sodium-ion salts within the glass. This process can result in undesirable irregular coverage resulting in pitted glass surfaces.
Another chemical tempering method involves substituting potassium ions with sodium ions in the surface layer of the glass plate. This is accomplished by spraying an aqueous solution of potassium ions upon the glass at a temperature of between 200° C. and 500° C. A disadvantage of this method is that it limits the application and production processes only to manufacturing plants set up to handle the extremely high heat.
See also U.S. Pat. No. 4,218,230 [August 1980] by Patrick M. Hogan. See also: U.S. Pat. Nos. 3,218,220, 3,287,201, 3,607,172, 3,743,491, 3,791,809, 3,798,013, 3,844,754, 4,055,703, 4,133,665, 4,922,467, and GBX Patent No. 966,734.
However glass tempering does not solve the hazardous issues of glass shattering, sometimes catastrophically, which is known by those skilled in the art.